Corrects 200+ instances of "it's" where it should've been "its" instead (#85169)

## About The Pull Request

it's - conjunction of "it" and "is"
its - possessive form of "it"

grammar is hard, and there were a lot of places where "it's" was used
where it shouldn't have been. i went and painstakingly searched the
entire repository for these instances, spending a few hours on it. i
completely ignored the changelog archive, and i may have missed some
outliers. most player-facing ones should be corrected, though
## Why It's Good For The Game
proper grammar is good

## Changelog
🆑
spellcheck: Numerous instances of "it's" have been properly replaced
with "its"
/🆑

code/game/objects/items/stacks/stack.dm

@@ -34,7 +34,7 @@
 	var/merge_type = null
 	/// The weight class the stack has at amount > 2/3rds max_amount
 	var/full_w_class = WEIGHT_CLASS_NORMAL
-	/// Determines whether the item should update it's sprites based on amount.
+	/// Determines whether the item should update its sprites based on amount.
 	var/novariants = TRUE
 	/// List that tells you how much is in a single unit.
 	var/list/mats_per_unit